Upon further inspection, it was found that the fuel oil secondary filter differential pressure sensor isolating valve on the port main engine had cracked, and this was causing the fuel spray. Approximately 1m3 of fuel was lost.
- The failure of the valve was caused by a combination of engine vibrations and the weight of assembly acting on the male threaded section of the brass valve;
- The pipe arrangement had been altered from the original set up because of pressure fluctuations – this interfered with the proper functioning of the sensor; the MSF notes that the long-term effect of this alteration was perhaps not properly assessed by the manufacturer prior to this alteration.
- The brass valve fitting is to be replaced with a stainless-steel equivalent to provide additional strength to the arrangement.
- A deflector plate was added above the valve in order that in the event of any future failure, any fuel spray will be prevented from contacting hot parts of the engine.
- Support arrangements for the assembly were investigated but deemed impractical.
Incidents such as this should act as a reminder to apply the management of change process and give due consideration to the short and long-term consequences of changes implemented on board. Many people viewing this change critically under a management of change, would question the long-term ability of the threaded section to support the weight of the full assembly. It is possible that this would have led to alternative solutions being considered and this high potential near miss being avoided.
The MSF recommends review of Management of Change process, in particular in association with the following extracts from the procedure;
- Technology: Changes to technology, systems and tools. Introduction of new systems and programs.
And the following considerations;
- The potential risks associated with the change.
- The arrangements to control the risks.
- Key safeguards which are in place to ensure HSE is maintained.
- The monitoring arrangements including the corrective action process.